02 Basic concepts Flashcards
How is the endocrine system different from the nervous
endocrine is anatomically discontinuous
both:
- major communications systems in the body
- integrate stimuli and responses to changes in external and internal environment
- crucial to coordinated functions of highly differentiated cells
How does the endocrine system broadcast hormonal messages
to all cells via secretion into blood and extracellular fluid
- slow and diffuse
- one gland potentially affects many or all body tissues
What are general principles of endocrine gland organization
Ductless
Highly vascular
Functional secretory cells are usually epithelial
What are the three types of endocrine organ arrangements
- Discrete glands (thyroid)
- Endocrine components of other organs (pancreas, gonads, ovaries, testis)
- Scattered cells throughout other organs (C cells in thyroid)
What are some basic characteristics of hormones
May have more than one target
active in low concentrations
more than one hormone may affect a target
May have same actions in more than one tissue, or opposite actions in two tissues
What are the 3 classes of hormones
Amino acids
Steroids
Proteins
What are characteriestics and examples of steroid hormones
- originate from a cholesterol precursor
- organs: ovaries, testis, adrenal cortex
- lipid soluble; bind to receptors inside the target cell
mineralcorticoids, glucocorticoids, testosterone, and estradiol
What are characteriestics and examples of protein hormones
- name indicates chemical structure
- wide variety of molecule sizes
- organs: anterior pituitary, thyroid, parathyroid, pancreas
- NOT lipid soluble; bind to surface receptors of the target cell
Insulin, prolactin, ADH, oxytocin, and parathormone
What are characteristics and examples of amino acid hormones (analogues and derivatives)
- name indicates chemical structure
- organs: thyroid, adrenal medulla
- most not lipid soluble (exception thyroid); bind to receptors on the surface of target cell
tyrosine derivatives = catecholamines (dopamine, epinephrine, norepinephrine) & thyroid hormones (Thyroxine T4, Triiodothyronine T3)
How are steroid hormones produced/stored
produced on demand and not stored
What types of organelles do steroid producing cells have the most of
SER, golgi
Where are amino acids, peptides, glycoproteins and protein hormones stored
Granules
ex: insulin in pancreas
What types of organelle do protein hormone producing cells have high levels of
RER
What type of cells do hormones have an affect on
target cells
Why do target cells respond to hormone
The cell has a receptor for the hormone
What are the two types of hormone receptors
Membrane receptors
Cytoplasmic receptors
What type of receptors do steroid hormones target
cytoplasmic/nuclear receptors
How does a steroid hormone change cell function
1) Bind to nuclear or cytoplasmic receptor
2) dimerizes
3) receptor hormone complex binds specific DNA sequences
4) Directly alters gene expression at the response element or promoter
5) produces a protein that elicits a biological response
How does hormonal action by plasma membrane receptors work
Hormone is 1st messenger
G proteins in cell membrane are activated
2nd messenger causes intracelluar change; may be cAMP, cGMP, Ca++
- used by hormones that cannot diffuse through the - -
plasma membrane: amines, peptides, proteins - hormone does NOT directly alter gene expression
name the endocrine glands of animals (9)
hypothalamus pineal gland pituitary gland thyroid gland parathyroid gland adrenal gland pancreas ovary testes
how does the nervous system send signals
- exerts point to point control through nerves
- electrical in nature
- fast
what are the principle functions of the endocrine system
- maintains homeostasis
- integrations and regulation of growth, metabolism, and development
- control, maintenance and instigation of sexual reproduction (including gametogenesis, fertilization, fetal growth, and development, and nourishment of the the newborn)
what are the 3 methods of cell communication between cells? Define them.
endocrine: hormone secreted into blood bonds distant target cells
paracrine: hormone acts locally by diffusing from its source to target cells in the neighborhood
autocrine: hormone acts on same cell that produced it
patterns of hormone secretion
some hormones secreted tonically (all the time); some secreted episodically (pulses)
frequency and amplitude of pulses vary in response to stimuli
diurnal (day, year, etc) and annual rhythms
what is the pattern of secretion of circulating cortisol
diurnal
strong pulse at 8am
moderate pulses at 1pm, 8pm, 6am
what is the pattern of secretion of gonadotropin in males and females
varies over a lifespan
increases during fetal development
childhood FSH > LH
puberty slowly increasing
sinusoidal rhythm during adult reproductive period (LH > FSH)
greater increase in females as they age but both increase (FSH > LH)
what are the control mechanisms used to regulate hormones
external stimuli (fright, cold, light cues) internal stimuli (blood sugar levels, hormonal signals from another gland) feedback loops
what disease is an example of the critical importantance of receptors
Type II Diabetes
caused by a lack of response NOT lack of hormone
How does hormonal action through intracellular receptors work?
characteristic of steroid and thyroid hormones
steroid hormones diffuse through plasma membrane
bind to nuclear (or sometimes cytoplasmic) receptor
receptor-hormone complex binds specific DNA sequences
directly alters gene expression
new mRNA and proteins made
new proteins change cell function
